In general, crude oil is extracted from an oil field, loaded into a crude oil tanker, and then transported to a destination at a long distance.
In a conventional crude oil tanker, a large amount of VOC occurs while crude oil is loaded into a crude oil storage tank of the crude oil tanker from a crude oil storage tank on land.
In order to supply crude oil to the crude oil storage tank of the crude oil tanker from the crude oil storage tank on the land, a supply pipe is horizontally installed at an upper part of the crude oil tanker, that is, over the crude oil storage tank of the crude oil tanker. The supply pipe has an end connected to the crude oil storage tank on land. In order to load the crude oil, which is supplied from the crude oil storage tank on land through the supply pipe, into the crude oil storage tank of the crude oil tanker, a load pipe is vertically connected to the bottom surface of the supply pipe. The load pipe vertically passes through the crude oil storage tank of the crude oil tanker and communicates with a lower part of the crude oil storage tank of the crude oil tanker. Furthermore, in order to distribute the crude oil, which is loaded into the crude oil storage tank of the crude oil tanker through the load pipe, into the crude oil storage tank of the crude oil tanker, a distribution pipe is installed at a lower end of the load pipe.
When the crude oil meets the vertical load pipe, that is, the upper end part of the load pipe while horizontally supplied from the horizontal supply pipe, the crude oil suddenly falls down. In this case, a flow cavitation may be caused at the upper end part of the load pipe by an excessive pressure drop which occurs while the flow rate of the crude oil increases. That is, when the static pressure of flow inside the load pipe is smaller than the vapor pressure of the flow, a flow cavitation occurs. When the static pressure of the flow is smaller than saturation pressure, flow evaporation occurs. As a result, the crude oil evaporates to generate VOC.
The VOC generated in such a manner are discharged to the air or sent back to the crude oil storage tank on land.
When discharged to the air, the VOC may cause serious environmental problems such as ozone layer damage. Furthermore, although the VOC are sent back to the crude oil storage tank on land, the VOC should be treated. In this case, the facility and cost are required for treating the VOC.